K2 + KPA100

[Ronald Stuy]

Hello,

 

I have a K2/100 and have some problems with the power.

The output power is jumping 5 watts all the time.

 

It doesn't matter the output, as soon the amplifier is switched on it goes
from 25 to 20 and back again for a few seconds and then 20 watts again.

It is the same even if the radio is just turned on or after a half hour
operating.

Without the amplifier it works fine, a steady 10 watts all the time, so I
don't think it is the input power.

 

I like to get some advice to solve this problem.

 

 

Regards Ronald

PA3EWP

 

 

 

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[Don Wilhelm-4]

  Ronald,

There is an application note on the Elecraft website that deals with
that behavior.
The "problem" is that for some K2s the power detection/power control
loop gain is too high, and the power will oscillate about the final
value and may take a significant amount of time to settle down.
The entire transmit chain is included in the power control loop, and the
gain of each K2 will vary due to several factors including the care
given during the build process and normal component tolerances.

The cure is to increase the value of R98 on the bottom of the RF board.
Use a temporary potentiometer (2k to 3K value is ideal).  Adjust the
potentiometer until the oscillation is reduced.  Be certain to monitor
the maximum power output on 10 meters where the transmit chain has the
lowest gain.
You may have to compromise between allowable 10 meter maximum power
reduction and the amount of power level oscillation at 40 meters (where
the transmit gain is normally highest).
When you have found the best setting of the pot, remove it, measure its
resistance and install the closest value standard resistor.

73,
Don W3FPR

On 10/19/2010 3:59 PM, Ronald Stuy wrote:

> Hello,
>
>
>
> I have a K2/100 and have some problems with the power.
>
> The output power is jumping 5 watts all the time.
>
>
>
> It doesn't matter the output, as soon the amplifier is switched on it goes
> from 25 to 20 and back again for a few seconds and then 20 watts again.
>
> It is the same even if the radio is just turned on or after a half hour
> operating.
>
> Without the amplifier it works fine, a steady 10 watts all the time, so I
> don't think it is the input power.
>
>
>
> I like to get some advice to solve this problem.
>
>
>
>
>
> Regards Ronald
>
> PA3EWP
>
>
>
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html